Two practical solutions for higher fuel mileage are
1. Hybrid, 2. Diesel.
Toyota made the biggest commitment to hybrid, hence Prius, Camry hybrids.
Ford is serious about hybrid, also.
VW/Audi made the biggest commitment to diesel.
Big three American brands are following, not leading like they once did.
At long, long last Chevy introduced their Cruze diesel sedan.
The only place to go now is Flintstone.
Lots of diesel in Europe. States wont let them in.